1. Field of the Invention
The present invention relates to a contour extraction apparatus for extracting the contour of an object captured, for example, by a visual sensor such as a CCD or infrared camera.
2. Related Art of the Invention
As techniques for extracting the contour of an object from an image captured by a CCD camera or the like, and specifically as contour extraction techniques resistant to noise, SNAKES described in "JOHO SHORI (Information Processing) Vol.30, No.9, pp.1047-1057," etc. and the image processing apparatus disclosed in Japanese Patent Unexamined Application No.319051 are known.
According to these techniques, when a rough contour of an object to be extracted is given in advance, the accurate contour of the object can be obtained by minimizing an energy function defined by the contour and image features. These techniques can be applied to multimedia equipment used, for example, for interactive image editing.
However, the above prior art techniques have had the problem that a plurality of objects cannot be extracted unless the number of objects to be extracted is specified in advance.
In SNAKES, it is required that a rough contour of an object be given in advance as an initial contour. As a result, when the number of objects or the number of images to be processed is large, the processing burden involved in setting the initial contours becomes excessive.
Furthermore, SNAKES has had the shortcoming that it cannot be applied for applications where the number of objects contained in an image needs to be detected automatically, as in the detection of the number of intruders in the case of a security system or in the detection of the number of room occupants in air-conditioning control.